Of course not, but they do reproduce and can do quite fast for animal propagated tree species. We are talking about 3.04 trillion trees. Even if the natural germination rates are low, it would still be significant enough to make a difference in the assertion this article uses as introduction.
Like I said, a lot of things have to be taken into account, including local deforestation and its effect on desertification. Higher averages temperatures are forcing forests to move to higher latitudes, but they are also clearing areas of growth that are not yet inhabited by humans and were far too cold before for trees to propagate to.
I'm not suggesting that there's not a problem with the way we use our forest resources, just that the oversimplification of the starting premise of the article doesn't help at all.
If self regeneration is low, it doesn’t matter what the absolute numbers are, they are still tiny compared to the level of deforestation.
Then there’s the attrition rate of forests, which is probably in the same order of magnitude as natural reforestation.
“Rate at which humans plant trees - rate at which humans destroy trees” is a good first order approximation of the general trends simply because the numbers are so large compared to all other factors.
In every environmental context, human action is the greatest impact by an order of magnitude simply because there are so many of us. For example, the greatest sources of methane in the environment are from human activities such as mining and cattle (64% according to USA EPA), way ahead of swamps and other natural sources.
Studies in Brazil suggest that natural reforestation is a process that takes between 60 years (some trees are back) to 4000 years (this patch has regenerated to be the same as the forest around it). It takes so much less time to clear a patch of forest than to regenerate, that the regeneration is a rounding error in calculations with two significant digits.